Cultured adult bovine aortic endothelial cells will be used to study the mechanisms involved in maintaining the integrity of the endothelium. Because of the importance of the extracellular matrix for endothelial integrity, a study of matrix-endothelial cell interactions is proposed. The effects of matrix and matrix components on endothelial migration in vitro will be studied. Fibronectin is a major component of the matrix, and its role in the synthesis and ultrastructure of marix will be studied. Finally, conditions which alter or inhibit matrix synthesis will be developed and then used to study subsequent effects on endothelial cells.